The present invention relates to electrical switch assemblies of the type actuated by a thermally responsive or temperature sensor. Devices of this type are well known for use in controlling service cycling of electrical appliances, as for example, heating and air conditioning equipment and appliances and heaters employed in household use. One particular application of thermostats for heaters is the application of heaters for waterfilled beds to provide individual sleeping comfort.
In applications for waterbed heaters, thermostats typically have employed a remote sensing bulb filled with liquid which is expansible through a capillary tube to a pressure capsule having an expansible diaphram. An intermediate lever is employed between the capsule diaphragm and the switching mechanism to provide the requisite amplification of diaphragm movement for effecting actuation of the switching mechanism for controlling the heating cycling.
In designing and manufacturing the aforesaid type of thermostats for waterbed heaters, problems have been encountered in positioning the intermediate lever between the capsule diaphragm and the switch actuator and providing the appropriate pivot or fulcrum for the lever and in providing for ease of calibration and range setting of the thermostat. Heretofore, the point of contact of the lever with the sensing capsule diaphragm has provided for the positioning of the lever member in the switch assembly by such expedients as a recess in the lever engaged by a raised portion of the diaphragm. However, in such arrangements, it has been found difficult to provide for accurate and repeatable set point adjustment operation of the thermostat in service due to wear of the adjustment mechanism or cam where the lever is pivoted and fixed at the point of contact with the diaphragm. Thus, it has been desired to find a way or means of positioning a switch actuating lever member in a thermostat in such a manner as to enable ease of manufacture, calibration and accurate repeatable adjustment of the actuation point within the range of desired temperatures.